Haskell相当于C的__LINE__ [英] Haskell equivalent of C's __LINE__

问题描述

（就像C的 __ LINE __ ）有没有办法在Haskell中获得行号/追溯信息？宏或Python的 traceback.extract_stack（））

这对于编写Haskell程序是有用的， C ++代码，这些代码将用注释告知Haskell行负责哪个C ++行。

Haskell示例：

  LINE#include< foo.h> - 这是第12行
：INDENTvoid Foo :: bar（）{}
 [LINE $blah（m_++ x ++，\++ x ++\）; 
 | x<  -  [Potato，Avocado] 
] 
  

会产生这个C ++代码：

  #include< foo.h> // gen.hs：12 
 void Foo :: bar（）{// gen.hs：13 
 blah（m_Potato，Potato）; // gen.hs：14 
 blah（m_Avocado，鳄梨）; // gen.hs：14 
} // gen.hs：13 
  

解决方案

您可以在Haskell中使用CPP __ LINE __ 编译指示。

  { - ＃LANGUAGE CPP＃ - } 
 
 main = do 
 printone 
 print __LINE__ 
 
 
 $ runhaskell A.hs 
one
 5 
  

另外，如果条件失败， Control.Exception.assert 函数将发出一个行号。

  import Control.Exception 
 
 main = do 
 printone
 assert False 
 printtwo
 
 
 $ runhaskell A.hs 
one
 A.hs：A.hs：5：5-10 ：断言失败
  

Is there a way to get line-number/traceback information in Haskell?

(like C's __LINE__ macro or Python's traceback.extract_stack())

That would be of use for me for writing Haskell program that generates C++ code, which would be notated with comments telling which Haskell line is responsible for which C++ line.

Haskell example:

LINE "#include <foo.h>" -- this is line 12
: INDENT "void Foo::bar() {" "}"
    [ LINE $ "blah(m_" ++ x ++ ", \"" ++ x ++ "\");"
    | x <- ["Potato", "Avocado"]
    ]

will generate this C++ code:

#include <foo.h>                  // gen.hs:12
void Foo::bar() {                 // gen.hs:13
  blah(m_Potato, "Potato");       // gen.hs:14
  blah(m_Avocado, "Avocado");     // gen.hs:14
}                                 // gen.hs:13

解决方案

You can actually use the CPP __LINE__ pragma in Haskell.

{-# LANGUAGE CPP #-}

main = do
    print "one"
    print __LINE__


$ runhaskell A.hs
"one"
5

Also, the Control.Exception.assert function will emit a line number if its condition fails.

import Control.Exception

main = do
    print "one"
    assert False $
        print "two"


$ runhaskell A.hs
"one"
A.hs: A.hs:5:5-10: Assertion failed

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